Magnetic type circuit breaker having air gap in face of face wound core structure for producing non-uniform magnetic field



Aug. 23, 1966 w. A. CARTER 3,268,699

MAGNETIC TYPE CIRCUIT BREAKER HAVING AIR GAP IN FACE OF FACE WOUND CORE STRUCTURE FOR PRODUCING NON-UNIFORM MAGNETIC FIELD Filed April 23, 1965 4 Sheets-Sheet 1 III/II II g5;

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BY 05 77901 5/, E4554: Qamgfir n Aug. 23, 1966 w. A. CARTER 3,268,699 MAGNETIC TYPE CIRCUIT BREAKER HAVING AIR GAP IN FACE OF PAGE WOUND CORE STRUCTURE FOR PRODUCING NON-UNIFORM MAGNETIC FIELD Filed April 23. 1965 4 Sheets$heet 3 A 4 5 I I a a w m. J12 m 3 Q m g M .w p Q 3 \fl/ \L 4 a 3 l/ 4 a I .J, 4, Q TILU. If A w a 5V R75? m ad L E 7 V v 4 m n we amp =7 kw 5W5 a I Q a mfl w 3 4w I m a WU ML 2 5 Aug. 23, 1966 w. A. CARTER 3,263,699

MAGNETIC TYPE CIRCUIT BREAKER HAVING AIR GAP IN FACE OF FACE WOUND CORE STRUCTURE FOR PRODUCING NON-UNIFORM MAGNETIC FIELD Filed April 25. 1965 4 Sheets-$heet 4 50 I I z \Q a s 4 I \J l k I I lid t3 r Q I INVENTOR. R I W/ZZ/flM 9. 5/7/9727? United States Patent 3 268 699 MAGNETIC TYPE Cll RClllT BREAKER HAVING AIR GAP 1N FACE 0F FACE WOUND CORE STRUCTURE FOR PRODUCING NDN-UNIFORM MAGNETIC FIELD William A. Carter, Devon, Pa, assignor t0 I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 23, 1965, Ser. No. 452,453 7 Claims. (Cl. 200147) This application is a continuation-in-part of application Serial No. 87,440, filed February 6, 1961 and application Serial No. 174,601, filed February 20, 1962 in the name of Wlliam A. Carter and assigned to the assignee of the instant invention.

This invention relates to a novel construction for the magnetic circuit of a magnetic air circuit breaker and more particularly to a magnetic circuit which has a physical separation therein.

Circuit breakers generally in use in present day switchgear systems are designed to include interrupting means which provide rapid extinguishment of electric arcs formed during the tripping operation. The interrupting means of the prior art are designed to include magnetic blowout means for urging electric arcs upward into the interrupting means. Such magnetic means include a blowout coil which is wound about an iron core. The iron core surrounds the perimeter of the interrupting means and acts to direct the magnetic field generated by the blow-out coil such that the direction of the magnetic field is transverse to the upwardly moving arc and the vertical faces of the interrupting means. Such apparatus is shown, for example, in FIGURE 6 of United States patent No. 3,070,681, entitled Face Wound Blow-Out Coil, issued December 25, 1962 to J. D. Wood and assigned to the assignee of the instant invention.

The are which is formed during the tripping operation of the circuit breaker is initially drawn between the breaker separating contacts. The are then transfers to a pair of spaced parallel arc runners which are positioned in the interrupting means. In travelling upward along the spaced parallel arc runners, the arc is confronted by a plurality of .spaced'parallel arc plates which provide a tortuous path for the arc resulting in subsequent cooling and extinguishment thereof.

Prior art circut breakers of the type described above suffer from three disadvantages which the instant invention eifectively eliminates. These three prior art problems are set out separately below, but it is to be understood that any one or more of these disadvantages may combine to reduce the total effectiveness of the circuit breaker in question.

(1) Prior art circuit breakers are designed such that the separating contacts are positioned immediately below the arc runners of the interrupting means. As will be seen in FIGURE 1 of the aforementioned Wood patent, the distance between the separating contacts and the rear arc runner 60 is substantially less than the distance between the separating contacts and the front are runner 62. Since the flux distribution of the magnetic field generated by the blow-out coil 70 and the unitary iron core structure 68 is generally uniform across the width of the interrupting arc chute, the transfer time from the separating contacts to the rear arc runner for one end of a drawn arc, is appreciably less than the transfer time for the other end of the arc in moving from the separating contacts to the front arc runner. Thus, the end of the are travelling up the rear arc runner leads the end of the are travelling up the front are runner and arrives at the top of its runner before the other end of the arc arrives at the top of its runner. This un- 3,258,599 Patented August 23, I966 equal rate of upward movement of the are within the arc chute causes one end of the arc to linger at the top of the rear arc runner and results in non-uniform deterioration of the arc runner. That is, the top of the rear arc runner is subjected to the burning of its respective end of the are for a longer period of time than is the top of the front are runner. The result of such burning is the liberation of substantial amounts of gaseous are products the pressure from which can destroy adjacent insulated components.

(2) The second prior art problem relates to the possibility of a reestablishrnent of an are between the arc runners of the circuit breaker after a current interruption. Specifically, and as will be seen in FIGURE 3 of the Wood Patent, 3,070,681, such prior art circuit interrupters include a unitary magnetic core surrounding the enclosed arc chute. Following the interruption of current, the voltage across the contacts of the circuit breaker attempt to become equal to the system voltage. This voltage also appears across the arc runners which are physically located inside the box-like magnetic circuit. The unitary construction of the magnetic core is found to influence the distribution of potential between the two runners placing a substantial portion of the potential gradient therebetween on a very small space 'between the arc runners. This condition causes ionization and breakdown of the air of this small space thereby putting the total concentrated potential gradient on the remaining non-ionized space between the runners. This overstress again results in ionization and breakdown, and progressively the entire remaining space between the arc runners becomes ionized and the arc is reestablished. Obviously such a reestablishment reignition is undesirable since it reest-ablishes the circuit which was to be interrupted and furthermore results in excessive deterioration of both the front and rear arc runners.

(3) The third problem of prior art circuit breakers is related to the second problem, above, in that it concerns the interrelationship of the arc runners and the unitary iron core such as shown in FIGURE 3 of the Wood patent. Specifically, it has been discovered that the iron core structure of the magnetic blow-out circuit will float to some predetermined potential depending upon the capacitive coupling between the iron core structure and the various energized elements within the circuit interrupter. That is to say, the iron core, because of its capacitive coupling, tends to float to the potential of nearby energized elements. Because of the capactive coupling throughout the unitary iron core, the entire core tends to float to a potential approaching that potential appearing on the rear arc runner. During dielectric tests, it has been found that because of the unitary core structure, the entire core is capacitively coupled to the rear arc runner thereby establishing a likelihood of flashover between the front are runner and/or the iron core and any grounded element which is in the immediate vicinity thereof. Again, it is obvious that such fiashover is highly undesirable from the viewpoint of both efficiency of circuit interruption and safety to personnel working near the circuit breaker.

The instant invention contemplates an arrangement whereby all three of the. above described prior art disadvantages may be eliminated. The novel structure of this invention will be discussed in the same order as the prior art problems enumerated above.

(1) With respect to the first problem, that of the nonuniform deterioration of the rear arc runner resulting from the difference in distances between the cooperating contacts and the front and rear arc runners respectively, the instant invention provides a novel non-unitary magnetic core in combination with a face wound blow-out coil which results in a non-uniform magnetic field in the portion of the interrupting arc chute which is encompassed by the iron core. The non-uniform magnetic field is greater in the vicinity of the front are runner than in the vicinity of the rear arc runner and consequently exerts a greater force on the lagging" end of the upwardly moving arc than is exerted on the leading end of the arc. Consequently, by the time the ends of the arc approach the tops of their respective arc runners, an imaginary line drawn between the ends is substantially parallel to the ground, and both ends of the arc reach the top of their respective runners at approximately the same time. Thus the nonunitary iron core in combination with the face wound blow-out coil eliminates the non-uniform deterioration of the tops of the arc runners which were prevalent in the prior art.

(2) With respect to the second problem, that of the unitary iron cores of the prior art causing an excessive concentration of the potential gradient in a small space between the front and the rear arc runners, the instant invention provides an iron core having an air gap therein. It has been discovered that this gap causes the potential gradient to be distributed relatively uniform throughout the arc chute and thus the possibility of re-strike caused by a non-uniform potential gradient has been eliminated.

(3) With respect to the third problem noted above, that of the possibility of a flashover from a point of high potential to a point of lower potential (which might include a grounded element) the non-unitary magnetic core discussed above results in a further advantage which virtually eliminates such flashover possibility. Specifically, by dividing the iron core into two sections which are electrically and mechanically isolated from one another, each section may float to potentials which are different from one another. Thus the front yoke will assume a lower potential difference from the front runner than was possible in the prior art because of the change in capacitive coupling brought about by the gap. Thus the possibility of a flashover between the front are runner and/ or the iron core and a grounded element in the immediate vicinity is substantially reduced.

Accordingly, it is an object of this invention to provide a magnetic structure which surrounds the arc chute of a magnetic air circuit breaker with a novel configuration to provide improved electrical and magnetic characteristics.

Another object of the instant invention is to provide novel magnetic structure for magnetic circuit breakers which is designed to redistribute the magnetic flux in the arc chute in a non-uniform manner, with the magnetic flux in the area near the front arc runner being greater than the magnetic flux in the area near the rear are runner.

A further object of the instant invention is to provide novel magnetic structure for a magnetic air circuit breaker which causes redistribution of the electrostatic potential gradient within the magnetic circuit to reduce the possibility of reestablishment of an arc.

Yet another object of this invention is to provide novel magnetic structure for a magnetic air circuit breaker which causes redistribution of potential stress between live par-ts and ground, particularly during impulse conditions.

These and other objects of the invention will become apparent from the following description when taken in conjunction with the following drawings, in which:

FIGURE 1 is a perspective view of a circuit breaker which includes the novel magnetic structure of the instant invention;

FIGURE 2 is a side plan view of the circuit breaker shown in FIGURE 1;

FIGURE 3 is a top plan view of the circuit breaker shown in FIGURE 1;

FIGURE 4 is a top plan view of the magnetic core structure used in the prior art;

FIGURES 5, 5a and 6 are top plan views of alternative embodiments of the iron core structure of the circuit breaker shown in FIGURE 1;

FIGURE 7 is a graph showing the magnetic flux dis- 4 tribution obtained by the magnetic core structure shown in each of the FIGURES 4, 5, 5a and 6;

FIGURE 8 is a schematic illustration of the circuit breaker shown in FIGURE 1 indicating the path of movement of an are which is drawn during circuit interruption;

FIGURE 9 is a top plan view of the magnetic core structure of circuit breakers of the prior art;

FIGURE 10 is a top plan view of an alternative embodiment of the iron core structure used in the circuit breaker of FIGURE 1; and

FIGURE 11 is a graph showing the percentage of potential gradient distributed within the arc chute of the circuit breaker of FIGURE 1 as a function of the distance from the rear arc runner of such circuit breaker.

Referring now to the drawings, FIGURE 1 shows a circuit breaker 10 which comprises upper and lower terminals 11 and 12, respectively, which are connected to the circuit to be protected.

Although FIGURE 1 shows a circuit breaker for protecting a three phase system, this showing is merely exemplary since my invention will function equally as well with either a lesser or greater number of phases. Terminals 11 and 12 are supported and isolated from one another by support means 13. Each lower terminal 12 is connected at its opposite end to movable bridge 14 (only a portion of which is shown in FIGURE 1). The opposite end of the movable bridge 14 has a main and arcing contact secured thereto which contacts engage the main and arcing contacts, respectively, mounted to upper terminals 11 (see FIGURE 2).

Interrupting means 15 is operatively positioned with respect to the cooperating contacts of circuit breaker 10 and consists of an arc chute 16 which is pivotally supported to support 13 by pivot means 17. Iron structure 18 which consists of a plurality of U-shaped lam-inations 19 and 20 (see FIGURE 3) surround the midportion of arc chute 16 and are rigidly secured thereto by fastening means 21. Magnetic core 18 has a gap 22 which separates U-shaped laminations 19 and 20. As shown in FIGURE 3, a like gap exists on the opposite face of arc chute 16. The operating mechanism (not shown) is mounted in the lower portion 23 of the carriage 24 upon which circuit breaker 10 is mounted. Movable bridge 14 is connected to the operating mechanism used in lower portion 23 by means of push rod 25.

FIGURE 2 shows the interior of circuit breaker 10 which consists of a movable bridge 14 which is pivotally mounted to lower terminal 12 by pivot means 26. Arci-ng contacts 27 and main contacts 28 are fixedly secured to the opposite end of movable bridge 14 and are positioned to engage arcing and main contacts 29 and 30, respectively, which are electrically connected to upper terminal 11.

Rear arc runner 32, which has an inwardly sloping lower portion 32a is secured to are chute 16 in any well known manner. Front are runner 3-3 is positioned in the right hand side of arc chute 16 (with respect to FIG- URE 2) and has an inwardly sloping portion 34. Conductive strips 35 and 36 serve as the path which links front are runner 33 to lower terminal 12.

Transfer gap 31 is secured to are chute 16 by pin means 31a which also secures the lower end of rear arc runner 32. Positioned between arc runners 32 and 33 are a plurality of arc plates 37 arranged in spaced parallel fashion. Arc plates 37 are supported by a ledge means 38 which are an integral part of the opposite faces of the interior of arc chute 16. It should be noted that arc plates 37 and are runners 32 and 33 may be supported and mounted by any well known means, such as the means shown for example in United States Patent 2,761, 934, entitled High Voltage Circuit Breakers, issued September 4, 1952 to J. D. Wood and assigned to the same assignee as the instant invention, or in United States Patent 2,941,060 entitled Arc Extinguishing Means For High Voltage Circuit Breaker, issued June 14, 1960, to

A. S. Caswell, and assigned to the same assignee as the instant invention. Since the arc plate and arc runner mountings play no part in the novelty of the instant invention, it should be understood that the above references are cited as merely exemplary.

Mounted immediately above arc plates 37 in arc chute 16 are a plurality of alternately disposed deflecting plates 39 which are positioned and secured by vertical positioning means 40. The alternate deflecting means 39 serve to prevent the comm-ingling and gathering of heated and ionized gases in the area immediately above the top of arc chute 16 so as to prevent a flashover from occurring between arc runners 32 and 33 immediately above are plates 37. The structure and operation of deflecting plates 39 is more fully explained in United States copending application Serial No. 779,419, entitled Alternate Lateral Deflecting Means for Arc Products, filed December 10, 1958 by William A. Carter, and now abandoned, and assigned to the same assignee as the instant invention.

My novel magnetic circuit, however, may be also utilized in arc chutes not containing deflection plates 39 since they play no part in the novelty of the instant invention.

Blow-out coil 41 (see FIGURES 2 and 3) is positioned along the vertical front face 16a of arc chute 16. Coil 41 is wound in a configuration to encompass contacts 27- 30 and are runners 32 and 33 so that these elements are under the influence of the strong magnetic field set up in FIGURE 3, the plane of the entire core structure may 5 be thought of as a plane which is transverse to the plane of the blow-out coil 41.

It can be seen from FIGURE 2 that the distance D between arcing contact 29 and the lower edge 32a of arc runner 32 is substantially less than the distance D between arcing contact 27 and the lower edge 34 of front arc runner 33. During the trip-ping operation of circuit breaker 10, the configuration of FIGURE 2 will cause an arc formed between arcing contacts 27 and 29 to transfer to rear arc runner 32 before transferring-to font arc runner 33. An illustration of this result may be seen in FIGURE 8 wherein end 304 of are 305 has travelled a substantial distance up inwardly sloping portion 32a of rear arc runner 32 while end 306 of are 305 has just reached the inwardly sloping portion 34 of front are runner 33. If are 305 were allowed to continue with end 304 leading end 306, end 304 would arrive at the topof arc runner 32 before end 306 would arrive at the top of front are runner 33. As noted previously, arc end 305 would then remain concentrated at the top of rear arc runner 32 and cause excessive burning of that are runner while waiting for are end 306 to catch up. This type of extinguishment would necessarily produce non-uniform deterioration of the arc runners 32 and 33 and reduce the effective life of the circuit interrupter 10.

As will be presently shown, iron core 18 has been designed to counterbalance the effect of the dissimilar distances D and D upon an upwardly moving arc by setting up a non-uniform flux pattern.

FIGURE 7 is a graph showing the magnetic flux distribution in Gauss measured within the area encompassed by the magnetic core structure 18 as a function of the distance in inches measured from the center of the arc chute. The magnetizing cur-rent used to energize blowout coil 41 was of the same magnitude throughout the test.

Curve 100 in FIGURE 7 shows the flux distribution using the prior art magnetic core 42 shown in FIGURE 4. It should be noted that this curve is substantially flat along its length and thus may be said to represent a uniform magnetic flux within the area encompassed by the magnetic core 42. This uniform flux distribution of curve 100 will therefore fail to counterbalance the effect of dissimilar distances D and D and an are travelling up the arc runners 32 and 33 will have its rear end leading its front end, resulting in the non-uniform deterioration discussed above.

Curve 101 of FIGURE 7 shows the flux distribution which is formed in arc chute with the non-unitary core design of FIGURE 5. The iron core 18 of FIGURE 5 comprises two U-shaped portions 19 and 20 separated by an air gap 22 preferably located approximately one-third of the distance of the arc chute away from the front are runner 33.

It will be observed that the flux density to the right of center line 0 is greater than the flux density to the left of the center line. This results in a greater magnetic force being exerted on an arc in the region of front arc runner 33 allowing the arc end 306 of FIGURE 8 to accelerate at a greater rate than are end 304 once such arc ends are under the influence of the split magnetic core. Thus arc end 306 catches up with are end 304 and both ends reach the tops of their respective runners at approximately the same time, thus eliminating the non-uniform deterioration prevalent in the prior art.

Curve 102 shows the flux distribution in the area encompassed by the magnetic core using the core configura tion shown in FIGURE 5a. It should be noted that the difference between the core configuration of FIGURE 5 and that in FIGURE 5a is the thickness of the front and rear ends 50 in FIGURE 5 and 51 in FIGURE 5a, the width of front and rear ends 50 being greater than the width of front and rear ends 51. The difference in width of the front and rear ends causes the flux density measured in the set up of FIGURE 5a, corresponding to curve 102, to be more intensified in area 307 than the flux density set up in FIGURE 5 shown by curve 101. Thus the core design of FIGURE 5w effectively counterbalances the difference between distances D and D to an even greater extent than that produced by the structure of FIGURE 5.

Curve 103 shows the flux density measured when using the core configuration shown in FIGURE 6 and shows another embodiment in which the difference in distance of D and D may be compensated for. From FIGURE 7 it can be seen that the magnetic flux in area 307 is somewhat less for curve 103 than for curve 102.

FIGURE 6 is distinguished from FIGURE 5 and 5a in that front and rear ends of iron core 43 and 43a, respectively, consist of air gaps 52 while the front and rear ends of FIGURES 5 and 5a consist of iron paths 50 and 51 connecting the sides 19 and 20 of iron core 18.

Obviously, any one of the configurations shown in FIG- URES 5, 5a and 6 may be used to accelerate the end of the are travelling up the front are runner once it enters the area encompassed by the magnetic core structure. Each of the configurations has its own advantageous characteristic (increasing magnitude of magnetic flux in area 307 of FIGURE 7), while each of the configurations also has its own undesirable characteristic (a dip in the area immediately to the right of the center line). However, it is noted that the dips caused by such configuration may only be eliminated by sacrificing a corresponding equal amount of the desirable intensified magnetic flux which occurs within the area designated 307 in FIGURE 7. Thus the particular magnetic core configuration chosen will depend upon the intensified magnetic flux necessary within the area designated 307 which in turn would be dependent upon the particular distances D and D for the circuit breaker chosen.

The next unusual result achieved by the air gaps 22 in iron core structure 18 was found to be in a redistribution of the electrostatic potential gradient within the arc chute 16 at all times, and particularly at a time following a current zero during interruption of low current.

It is well known that following the interruption of a current, the voltage across the contacts of the circuit breaker will attempt to become equal to the system voltage. This voltage also appears across the arc runners such as 320 and 330 of the prior art configuration of FIGURE 4 which are physically contained within the boxlike magentic circuit of unitary iron core 42.

Close proximity of magnetic core 42 influences the distribution of potential gradient between the arc runners 320 and 330 whereby tests have shown that approximately 85% of the total potential gradient between these runners can exist in 15% to 215% of the space between these runners. This condition can cause a breakdown of the air in this small space, thereby placing the total potential on the remaining space. The high potential stress on the remaining space again results in ionization and breakdown, and progresses until the entire space becomes ionized so that reestablishment of the arc occurs.

The distribution of potential gradient versus the distance in inches from the rear arc runner for prior art iron core configurations such as those shown in FIGURE 9 and FIGURE 4 is shown on the graph of FIGURE 11, The ideal potential gradient distribution is shown by the straight line 130 in FIGURE 11 and shows that the percentage of potential gradient distributed between the front and rear arc runners should be uniform and a function of distance. It is noted that in each of these prior art core structures of FIGURES 9 and 4, respectively, the rear arc runner 320 is encompassed by either substantially all, or all of the iron core structures 117 and 42, respectively.

The result of these prior art configurations may be clearly seen in FIGURE 11 wherein curves 127 and 128, corresponding respectively to FIGURES 9 and 4, show the percentage of potential gradient within the arc chute to be non-uniformly distributed therein. The high percentage of potential gradient which may appear at one concentrated area, for example, at a distance of 4 inches from the rear arc runner for curve 127, and at a distance of 10 inches from the rear arc runner for cuve 128 has been found to overstress the air at these points and begin the process of reestablishment of the arc which was described above.

By providing gaps 131 and 132 in the iron core structure 119 shown in FIGURE 10, curve 129 (corresponding to FIGURE 10) is seen to more closely approach the curve 130 which represents the ideal potential gradient distribution. Thus with the potential gradient more uniformly distributed throughout the arc chute, the possibility of potential gradient concentration at one point within the arc chute is reduced and thus the possibility of breakdown therein and reestablishment between the runners is substantially reduced.

It has been found that a minimum gap width of approximately 4 inches is necessary to achieve such gradient distribution. It has also been found that such gap may be placed virtually anyhwere along the face of the iron core structure. However gaps 131 and 132 would be preferably located at approximately one-third the distance of the total length of the arc chute from the front are runner 33. By choosing this particular location, the advantageous result of increasing the magnetic field in the area of the front are runner (see FIGURE 7) may be accomplished at the same time as the uniform distribution of potential gradient throughout the chute.

The final advantage which was obtained with the novel split core construction of FIGURES 5, 5a, 6 and 10 was a redistribution of potential stress between live parts of the system and ground, particularly during impulse conditions. By way of example, in FIGURE 2, the circuit interrupter 10 is illustrated as being contained within the schematically shown housing 133. The housing 133 is connected to ground potential as are many of the other structural elements within housing 133 which are used for support of the circuit interrupter 10.

It has been discovered that unitary iron core structures "of the prior art will float to some predetermined potential, depending upon the capacitive coupling between the iron core structure and the various energized elements within the system. By way of example, consider the iron core 18 of FIGURE 2 to be of unitary construction rather than split in two sections as shown.

The blow out coil 41 of FIGURE 2 is connected to rear terminal 11 which could be at a high potential. The same blow-out coil has portions positioned adjacent elements such as the magnetic core structure 18. By means of capacitive coupling through the blow-out coil 41, it is possible for the iron core 18 to assume the potential which appears on the terminal 11, and thus there is a likelihood of a flashover from the iron core 18 to the grounded housing 133.

I "have found that by separating the magnetic structure into two portions 19 and 20, as illustrated in FIGURES 1, 3, 5, 5a, 6 and 10, the BIL rating of the system is considerably increased. That is to say the magnetic core structure will now remain insulated with respect to the grounded housing 133, whereas when the core was formed of a single unitary member, there would be a flashover for the same impulse test.

The reason for this phenomena is apparently that because of the gaps 22 (see FIGURES 1, 5, 6) each of the core sections 19 and 20 is free to assume its own respective floating potential, whereby under high dielectric stress such as during impulse testing, the potential on the front yoke section 19 is not necessarily capacitively coupled to the same high potential as the rear yoke section 20 which is spaced closer to the terminal 11. Thus the front yoke section 19 is free to float to some intermediate potential between ground potential and the potential appearing on the rear yoke section 20; and therefore the likelihood of a flashover from front yoke section 19 of iron core 18 to the grounded housing 133 is substantially reduced.

It is noted that the front yoke portion 19 of core 18 may be isolated from rear yoke portion 20 by placing the gap 22 anywhere in the magnetic core 18. However, in the preferred embodiment such gap would be located approximately one-third of the length of the arc chute away from the front are runner in order to achieve the aforementioned highly desirable intensification of magnetic flux in the area of the front arc runner.

Thus there has been described a novel magnetic air circuit breaker which includes a face wound blow-out coil and a non-unitary iron core. The gap in the iron core etfectuates a uniform distribution of potential gradient within the arc chute of such breaker thus eliminating the possibility of restrike and furthermore allows each isolated portion of the magnetic core to assume a potential independent of one another to reduce the possibility of flashover.

Furthermore, by positioning the aforementioned gap at a predetermined location oif-center along the arc chute, the resultant magnetic flux within the arc chute is found to be non-uniform, and specifically greater in the area near the front arc runner than in the area near the rear arc runner. Such intensification of the magnetic flux near the front are runner allows the ends of an arc moving upwardly through the arc chute to arrive at the tops of their are runners at substantially the same time, thereby eliminating non-uniform deterioration of the tops of the arc runners.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the examples of construction and the combination and arrangement of parts may be resorted to Without departing from the sphere and scope of the invention as hereinafter claimed.

What is claimed is:

1. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a pair of arc runners positioned at said opposite interior ends of said are chute, said pair of cooperating contacts being closer to one of said are runners than the other of said are runners, blow-out means including a blow-out coil and an iron core, said blow-out coil being positioned along said first face of said are chute, said iron core being substantially rectangular in shape and being positioned to surround the outer perimeter of said are chute, the plane of said iron core being transverse to the plane of said blow-out coil, said iron core having at least one air gap positioned offcenter along said first face of said are chute, said blowout means generating a non-uniform magnetic field in that portion of said are chute surrounded by said iron core.

2. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an arc drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a front and rear arc runner positioned at said opposite interior ends of said are chute, said pair of cooperating contacts being closer to said rear arc runner than said front are runner, blow-out means energized by said are for urging said are into said are chute, said blow-out means including a face wound blow-out coil and an iron core, said blow-out coil being positioned along said first face of said are chute, said iron core being substantially rectangular in shape and being positioned to surround the outer perimeter of said are chute, the plane of said iron core being transverse to the plane of said blow-out coil, said iron core having at least one air gap positioned off-center along said first face of said are chute, said iron core comprising a plurality of stacked rectangular shaped laminations, said blow-out means generating a greater magnetic field in the area near the front are runner than in the area near the rear arc runner.

3. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, blow-out means energized by said are for urging said arc upward through said are chute, said blow-out means including a blow-out coil and an iron core, said blow-out coil being Wound along said first face of said are chute, said core being positioned around the periphery of said are chute, the plane of said core being transverse to the plane of said blow-out coil, said core having first and second gaps positioned off-center along said first and second faces, respectively, and third and fourth gaps each positioned along faces of said are chute adjacent to the said first face, a first and second arc runner secured at said opposite interior ends of said are chute, said pair of cooperating contacts being closer said second arc runner than said first arc runner, said first and second gaps being positioned closer to said first arc runner than said second arc runner, said blow-out means generating a greater magnetic field in the area near said first arc runner than in the area near said second arc runner to cause the ends of said are to reach the tops of said are runners at substantially the same time, said iron core comprising a plurality of stacked rectangularly shaped laminations, each of said laminations being formed of ferromagnetic material.

4. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a front and rear arc runner positioned at said opposite interior ends of said are chute, said pair of cooperating contacts being closer to said rear arc runner than said front arc runner, blow-out means energized by said are for urging said are into said arc chute, a magentic blow-out circuit including a blow-out coil and an iron core, said blow-out coil being mounted along said first face of said arc chute, said core being positioned to surround the periphery of said are chute, said core having sides which are parallel to said first face and sides which are perpendicular to said first face, the plane of said core being transverse to the plane of said blow-out coil, said iron core having a first gap located oifcenter along said first face of said are chute and a second gap located off-center along said second face of said chute, said first and second gaps being closer to said front are runner than said rear arc runner, the cross-section of said iron core being greater along said sides of said core parallel to said first face of the arc chute than the cross-section of said sides of said core which are perpendicular to said first face, said magnetic blowout circuit generating a greater magnetic field in the area near the front arc runner than in the area near the rear arc runner.

5. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a front and rear are runner positioned at said opposite interior ends of said are chute, said pair of cooperating contacts being closer to said rear arc runner than said front are runner, blow-out means energized by said arc for urging said are into said arc chute, said blow-out means including a blow-out coil and an iron core, said blow-out coil being Wound along said first face of said are chute, said core being positioned to surround the periphery of said are chute, said core having sides which are parallel to said first face and sides which are perpendicular to said first face, the plane of said core being transverse to the plane of said blow-out coil, said iron core having a first gap located off-center along said first face of said are chute and a second gap located off-center along said second face of said are chute, said first and second gaps being located closer to said front are runner than said rear arc runner, the cross-section of said iron core being greater along said sides of said core parallel to said first face of the arc chute than the cross-section of said sides of said core which are perpendicular to said first face, said first and second gaps being positioned from said front are runner a distance representing approximately one-third of the length of said first face of said arc chute.

6. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a pair of arc runners positioned at said opposite interior ends of said are chute, said pair of cooperating contacts beingcloser to one of said are runners than the other of said are runners, blow-out means energized by said arc for urging said are into said are chute, said blow-out means including a blow-out coil and an iron core, said blow-out coil being positioned along said first face of said are chute, said iron core being substantially rectangular in shape and being positioned to surround the outer perimeter of said are chute, the plane of said iron core being transverse to the plane of said blow-out coil, said iron core being formed of a first and second portion, said first and second portions defining a closed magnetic circuit, said first and second portions being electrically and mechanically isolated with respect to one another to form a vertically aligned gap therebetween, said first and second portions having U-shaped configurations, each of said U-shaped configurations including parallel legs having first ends, said first ends of the legs of said U-shaped configurations being spaced from one another, said vertically aligned gap being closer to said other of said arc runners than said one of said are runners to generate a greater magnetic field in the area near the said other are runner than in the area near said one are run ner while at the same time efiectuating a uniform potential gradient between said are runners and further allowing said first and second portions to capacitively assume electric potentials different from one another.

7. A circuit breaker comprising a pair of cooperating contacts, a substantially rectangular arc chute positioned to extinguish an are drawn between said contacts upon separation thereof, said are chute having a pair of opposite interior ends and first and second faces joining said opposite interior ends, a pair of arc runners positioned at said opposite interior ends of said are chute, said pair of cooperating contacts being closer to one of said the plane of said blow-out coil, said iron core being formed of a first and second portion, said first and second portions defining a closed magnetic circuit, said first and secondportions being electrically isolated with respect to one another'to form a vertically aligned gap therebetween, said gap being closer to said other of said are runners than said one of said arc runners to generate a greater magnetic field in the area near the said other arc runner than in the area near said one are runner while at the same time eifectuating a uniform potential gradient between said are runners and further allowing said first and second portions to capacitively assume electric potentials different from one another, said gap having a minimum width of approximately four inches.

References Cited by the Examiner UNITED STATES PATENTS 2,337,949 12/1943 Walle 200--147 2,635,158 4/1953 Peter 200147 2,761,933 9/1956 Latour 200147 2,777,036 1/1957 Frink etv al. 200147 2,831,946 4/1958 Wood 200-147 3,070,681 12/ 1962 Wood 200-147 FOREIGN PATENTS 704,611 3/1965 Canada. 1,039,119 9/1958 Germany.

705,463 3/ 1954 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examiner. 

1. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS, A SUBSTANTIALLY RECTANGULAR ARC CHUTE POSITIONED TO EXTINGUISH AN ARC DRAWN BETWEEN SAID CONTACTS UPON SEPARATION THEREOF, SAID ARC CHUTE HAVING A PAIR OF OPPOSITE INTERIOR ENDS AND FIRST AND SECOND FACES JOINING SAID OPPOSITE INTERIOR ENDS, A PAIR OF ARC RUNNERS POSITIONED AT SAID OPPOSITE INTERIOR ENDS OF SAID ARC CHUTE, SAID PAIR OF COOPERATING CONTACTS BEING CLOSER TO ONE OF SAID ARC RUNNERS THAN THE OTHER OF SAID ARC RUNNERS, BLOW-OUT MEANS INCLUDING A BLOW-OUT COIL AND AN IRON CORE, SAID BLOW-OUT COIL BEING POSITIONED ALONG SAID FIRST FACE OF SAID ARC CHUTE, SAID IRON CORE BEING SUBSTANTIALLY RECTANGULAR IN SHAPE AND BEING POSITIONED TO SURROUND THE OUTER PERIMETER OF SAID ARC CHUTE, THE PLANE OF SAID IRON CORE BEING TGRANSVERSE TO THE PLANE OF SAID BLOW-OUT COIL, SAID IRON CORE HAVING AT LEAST ONE AIR GAP POSITIONED OFFCENTER ALONG SAID FIRST FACE OF SAID ARC CHUTE, SAID BLOWCUT MEANS GENERATING A NON-UNIFORM MAGNETIC FIELD IN THAT PORTION OF SAID ARC CHUTE SURROUNDED BY SAID IRON CORE. 